Ontario’s Labour Relations Board is hearing an application today asking for the ongoing high school teacher strikes to be declared illegal.More than 70,000 high school students in Durham, Peel and Sudbury are out of school as a result of strikes, some for almost four weeks.The three affected school boards believe the Ontario Secondary School Teachers Federation is staging local strikes to put pressure on negotiators at the provincial level, which isn’t allowed under a new bargaining system introduced last year.Under that system, school boards negotiate local issues, while larger issues like salaries and class sizes are discussed for the entire province.The head of the union, however, says they followed all the necessary steps before sending the teachers on strike.